(Hybrid) sphygmomanometers for clinic blood pressure ... - Nature

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Jan 26, 2012 - An accurate measurement of blood pressure (BP) has important implications for clinical decision making, as it is the basis for a.
Journal of Human Hypertension (2012) 26, 211 - 213 & 2012 Macmillan Publishers Limited All rights reserved 0950-9240/12 www.nature.com/jhh

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Automated-auscultatory (Hybrid) sphygmomanometers for clinic blood pressure measurement: a suitable substitute to mercury sphygmomanometer as reference standard? G Parati1,2 and JE Ochoa1,2 Journal of Human Hypertension (2012) 26, 211 -- 213; doi:10.1038/jhh.2011.119; published online 26 January 2012 An accurate measurement of blood pressure (BP) has important implications for clinical decision making, as it is the basis for a reliable diagnosis of hypertension and allows assessing whether and how much the goals of antihypertensive treatment are being achieved. Mercury sphygmomanometer, using the auscultatory method, has long been regarded as the reference standard for this purpose, because most evidence on the cardiovascular risk associated with elevated BP levels, as well as on the benefits of BP lowering, comes from studies using this method.1,2 Indeed, in spite of the mercury sphygmomanometer having practical and technical limitations, and requiring specific training and regular maintenance, when BP is measured by a trained observer using the auscultatory technique, the mercury sphygmomanometer is still regarded as an accurate device for indirect BP measurement. In recent years, however, growing awareness on the detrimental consequences of mercury for human health and for the environment has led to progressively ban its use in measuring devices in many countries, promoting at the same time the search for viable alternatives.3 In such a context, recent recommendations from regulatory authorities (Scientific Committee on Emerging and Newly Identified Health Risks, SCENIHR, Mercury Sphygmomanometers in Healthcare and the Feasibility of Alternatives, 2009)4 have proposed to confine the use of mercury sphygmomanometers to ongoing epidemiological studies and to validation studies of new devices for BP measurement, where it is still currently employed as a reference standard. Indeed, the SCENIHR group was not only worried about the risk associated with use of mercury devices, but also concerned that the replacement of mercury-containing sphygmomanometers by alternative mercury-free devices might be responsible for problems in the clinical management of high BP conditions, either by endangering proper health care in specific groups of patients, and/or by undermining long-term epidemiological studies for public health, where a sudden change in the BP measuring method in the course of these studies might introduce possible biases and errors in the final outcome. The SCENIHR experts were also concerned about the need to consider both availability and quality of alternative devices for BP measurement. Among mercury free alternatives for conventional BP measurement, the most commonly available ones are those based on use of an aneroid manometer or of an electronic pressure transducer. These alternative sphygmomanometers use the auscultatory approach for BP determination, and therefore have the advantages and limitations, characteristic of the auscultatory technique and related to the observer’s performance, which also apply to the mercury sphygmomanometer. It has to be emphasized, however, that aneroid

manometers would require frequent calibration, every 6 months, in absence of which their accuracy becomes questionable.5 Additional solutions for mercury-free BP measurements are provided by use of non-auscultatory devices based on the oscillometric technique. Oscillometric instruments, however, operate under a completely different principle and are thus not considered as true ‘alternatives’ to mercury sphygmomanometers. Moreover, even validated oscillometric devices may have accuracy limitations in special patient groups, including patients with arrhythmias, diabetes, pre-eclampsia and the elderly,5 in whom, conversely, validated non-mercury auscultatory alternatives can be more appropriate.4 After a careful evaluation of the available evidence related to the best approach to BP measurement in a clinic setting, SCENIHR experts have come to the conclusion that when BP is measured by a trained observer using the auscultatory technique, the mercury sphygmomanometer or a validated auscultatory alternative currently remains the most accurate approach to indirect BP measurement, especially for certain patient groups. Their conclusions on this debated issue, together with the recommendation that, for all BP measuring devices, regular maintenance is of primary importance, are summarized in a document available on the EU website.4 On the basis of such a report, the current consensus with regard to BP measurements in a clinic setting is summarized in Table 1. As a general comment, all the various alternatives to the mercury sphygmomanometer currently available have widely varying levels of accuracy, emphasizing the importance of clinical validation; moreover, at present there is no general agreement on which technique will best replace mercury for BP measurement in clinical practice or as a reference standard for validation of BP devices. Use of hybrid (automated -- auscultatory) sphygmomanometers, has been proposed as a promising alternative to auscultatory readings by the classic mercury manometer, as this approach allows combining the best features of auscultatory readings obtainable with a mercury manometer with those of automated measurements provided by electronic devices. When hybrid devices are used listening with a stethoscope to the Korotkoff sounds in the same way as with mercury sphygmomanometers, this is made possible by the combination of an accurate electronic pressure transducer with either a digital ‘mercury-like’ column or a display with digit numbers for BP readings by the clinician, in substitution of the mercury column.6 In a recent study, one of these prototypes, the Nissei DM3000 (Nissei Healthcare, West Sussex, UK) device, was shown to be accurate in measuring BP either by selecting automated or manual (that is, auscultatory) modes.7 By applying state-of-the-art validation criteria, a study by Stergiou GS, et al.8 published in the current issue of the Journal of Human Hypertension, provides further data supporting not only

1 Department Cardiology, Istituto Auxologico Italiano, IRCCS, Milano, Italy and 2Department Clinical Medicine and Prevention, University Milano-Bicocca, Milan, Italy. Correspondence: G Parati, S Luca Hospital, Istituto Auxologico Italiano, Piazza Brescia, 20 Milano 20149, Italy. E-mail: [email protected]

Commentary

212 Table 1. Indications for blood pressure measurement in a clinic setting (based on SCENIHR - EU experts report 4) Blood pressure measurement in the clinic. methodological issues  Mercury sphygmomanometers should remain available as reference standards for clinical validation studies of nonmercury-containing BP measurement devices, until an alternative standard is developed and internationally recognized.  On-going, long-term, epidemiological studies currently using mercury sphygmomanometers should continue using this approach to BP measurement.  Alternative mercury-free devices using auscultation have similar limitations as the mercury sphygmomanometers regarding the observer bias and the intrinsic limitations of the auscultatory method.  Oscillometric automated instruments, commonly used at patients’ home, should be increasingly considered to replace the mercury sphygmomanometers also in a clinic setting.  The continuing accuracy of validated oscillometric devices with long-term use in a clinic setting needs to be demonstrated.  The oscillometric technique can be inaccurate in some patients (for example, arrhythmias), while a specific validation is needed in special populations (12).

the accuracy of auscultatory readings by the Nissei DM3000 device for BP measurement in a clinic setting, but also the potential of this device to suitably replace mercury manometers as a standard approach for validation of novel BP measuring devices. The study has the merit of applying for the first time in this context a modified version of the latest European Society of Hypertension International Protocol (ESH-IP) revision for validation of BP measuring devices in adults, published in year 2010.9 This recently revised protocol, compared with the previous ESH-IP published in year 200210 was further improved to prevent protocol violations and to ensure complete data reporting. To test the accuracy of this hybrid device in its auscultatory mode, Stergiou et al.8 have introduced a number of changes in the ESH-IP 2010 protocol, aimed at applying more stringent validation criteria, which allowed simultaneous (rather than sequential) auscultatory BP measurements being performed both with Nissei DM3000 device and with two standard mercury sphygmomanometers. This was done by two observers (blinded both with regard to each other’s readings and to the hybrid device readings), and by an independent supervisor, who also controlled that the deflation rate was kept at about 2 mm Hg per second to guarantee optimal auscultatory BP measurements. The tested hybrid device in its auscultatory mode showed the same level of accuracy as the mercury sphygmomanometers (only 2 of 99 systolic and 1 of the respective diastolic readings differed by 45 mm Hg from the reference method), and a higher level of precision compared with previously validated automated oscillometric devices.11 The authors could thus corroborate the previously suggested validity of this device in measuring BP levels, further supporting the proposal to use it in clinic settings in replacement of mercury sphygmomanometers. The results of the study by Stergiou et al.8 also support the suggestion that this device could be suitable for validation studies, by showing that its level of accuracy was the same as that of the mercury sphygmomanometers. In particular, the study was based on the concept that, for a given device to be a perfect substitute of the mercury sphygmomanometer, the differences between the tested device and the mercury sphygmomanometer should be similar to differences between two mercury sphygmomanometers. Stergiou et al.8 did indeed show that the differences between auscultatory BP measurements obtained with the tested device and with mercury manometers were almost the same as the differences between BP measurements performed with two mercury sphygmomanometers in Journal of Human Hypertension (2012) 211 - 213

the same subjects. This was the case when focusing either on differences in mean BP values and in their SD, or on the number of measurements with BP discrepancies between devices within 2 and 4 mm Hg. It has also been suggested that besides providing accurate measures of BP, a potential substitute of mercury sphygmomanometer to be indicated as a new gold standard reference, should resemble as closely as possible the classic device also in the way it is being used.6 Hybrid sphygmomanometers such as the one tested by Stergiou et al.8 seem to suit both conditions, since they turned out to be highly accurate (as confirmed by the study of Stergiou et al.8 on the background of previous evidence) and because they allow physicians to take BP readings in the same way as with mercury devices through use of a digital, ‘mercury-like’, column. An additional reason supporting the clinical interest of the hybrid device tested in the present study is that, as previously mentioned, it also offers the possibility to perform automated BP measurements with the oscillometric approach. This mode of action, which may potentially allow eliminating the problem of terminal digit preference and operators’ bias, was, however, not evaluated in the study by Stergiou et al.8 Finally, the potential ability of the Nissei DM3000 device to offer accurate measurements in different clinical conditions is in theory further supported by the possibility it offers to perform BP measurements at different preset deflation rates (2.5, 4.5 or 6.5 mm Hg per second). However, also this additional interesting feature of the Nissei DM3000 device was not tested in the validation study by Stergiou et al.,8 which only focused on the device manual auscultatory mode at a deflation rate of 2 mm Hg per second, operated by a trained operator. In conclusion, on the background of the SCENIHR experts recommendations, because of its dedicated design and close adhesion to an enhanced version of the recently published ESH-IP 2010 protocol, the results provided by the present study seem to represent solid evidence to propose the tested hybrid device in its auscultatory mode as a suitable substitute to mercury for BP measurement in clinical settings, but also as a reference standard for validation of novel BP devices. This paper also offers an example for future validation studies in this specific field, indicating which key research questions are to be addressed in order to provide physicians with useful information in their daily practice. It has to be emphasized, however, that a complete assessment of the whole clinical applicability of the Nissei DM3000 device, in particular for what concerns its ability to yield oscillometric readings or the clinical relevance of selecting different cuff deflation rates, remains to be assessed by future investigations.

CONFLICT OF INTEREST The authors declare no conflict of interest.

REFERENCES 1 O’Brien E, Asmar R, Beilin L, Imai Y, Mallion JM, Mancia G et al. European Society of Hypertension recommendations for conventional, ambulatory and home blood pressure measurement. J Hypertens 2003; 21(5): 821 - 848. 2 Pickering TG, Hall JE, Appel LJ, Falkner BE, Graves J, Hill MN et al. Recommendations for blood pressure measurement in humans and experimental animals: Part 1: blood pressure measurement in humans: a statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Hypertension 2005; 45(1): 142 - 161. 3 Mercury in measuring devices (amendment of Council Directive 76/769/EEC) Directive 2007/51/EC of the European Parliament and of the Council of 25 September 2007. http://ec.europa.eu/enterprise/sectors/chemicals/documents/ reach/archives/market-restrictions/amendments_en.htm. 4 SCENIHR (Scientific Committee on Emerging and Newly Identified Health Risks). Mercury Sphygmomanometers in Healthcare and the Feasibility of Alternatives.

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23 September 2009. http://ec.europa.eu/health/ph_risk/committees/04_scenihr/ docs/scenihr_o_025.pdf. O’Brien E, Waeber B, Parati G, Staessen J, Myers MG. Blood pressure measuring devices: recommendations of the European Society of Hypertension. BMJ 2001; 322(7285): 531 - 536. Pickering TG. What will replace the mercury sphygmomanometer? Blood Press Monit 2003; 8(1): 23 - 25. Tasker F, De Greeff A, Shennan AH. Development and validation of a blinded hybrid device according to the European Hypertension Society protocol: Nissei DM-3000. J Hum Hypertens 2010; 24(9): 609 - 616. Stergiou GS, Karpettas N, Kollias A, Destounis A, Tzamouranis D. A perfect replacement for the mercury sphygmomanometer: the case of the hybrid blood pressure monitor. J Hum Hypertens 2012; 26(4): 220 - 227.

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9 O’Brien E, Atkins N, Stergiou G, Karpettas N, Parati G, Asmar R et al. European Society of Hypertension International Protocol revision 2010 for the validation of blood pressure measuring devices in adults. Blood Press Monit 2010; 15(1): 23 - 38. 10 O’Brien E, Pickering T, Asmar R, Myers M, Parati G, Staessen J et al. Working Group on Blood Pressure Monitoring of the European Society of Hypertension International Protocol for validation of blood pressure measuring devices in adults. Blood Press Monit 2002; 7(1): 3 - 17. 11 dabl Educational Trust. Devices for blood pressure measurement. http:// wwwdableducationalorg. 12 Parati G, Stergiou GS, Asmar R, Bilo G, de Leeuw P, Imai Y et al. European Society of Hypertension guidelines for blood pressure monitoring at home: a summary report of the Second International Consensus Conference on Home Blood Pressure Monitoring. J Hypertens 2008; 26(8): 1505 - 1526.

Journal of Human Hypertension (2012) 211 - 213